Convert IFace Rename Errors (#19927)

Converts uses of TcRnUnknownMessage in GHC.Iface.Rename.

Closes #19927

9 files changed, 57 insertions, 20 deletions

diff --git a/compiler/GHC/Iface/Rename.hs b/compiler/GHC/Iface/Rename.hs
index ce49c7c976..e2a89570d3 100644
--- a/compiler/GHC/Iface/Rename.hs
+++ b/compiler/GHC/Iface/Rename.hs
@@ -68,14 +68,12 @@ tcRnModExports x y = do
     hsc_env <- getTopEnv
     tcRnMsgMaybe $ rnModExports hsc_env x y
 
-failWithRn :: SDoc -> ShIfM a
-failWithRn doc = do
+failWithRn :: TcRnMessage -> ShIfM a
+failWithRn tcRnMessage = do
     errs_var <- fmap sh_if_errs getGblEnv
     errs <- readTcRef errs_var
     -- TODO: maybe associate this with a source location?
-    let msg = mkPlainErrorMsgEnvelope noSrcSpan $
-              TcRnUnknownMessage $
-              mkPlainError noHints doc
+    let msg = mkPlainErrorMsgEnvelope noSrcSpan tcRnMessage
     writeTcRef errs_var (msg `addMessage` errs)
     failM
 
@@ -329,11 +327,8 @@ rnIfaceGlobal n = do
                         -- TODO: This will give an unpleasant message if n'
                         -- is a constructor; then we'll suggest adding T
                         -- but it won't work.
-                        Nothing -> failWithRn $ vcat [
-                            text "The identifier" <+> ppr (occName n') <+>
-                                text "does not exist in the local signature.",
-                            parens (text "Try adding it to the export list of the hsig file.")
-                            ]
+                        Nothing ->
+                          failWithRn $ TcRnIdNotExportedFromLocalSig n'
                         Just n'' -> return n''
        -- Fastpath: we are renaming p[H=<H>]:A.T, in which case the
        -- export list is irrelevant.
@@ -356,12 +351,8 @@ rnIfaceGlobal n = do
                             $ loadSysInterface (text "rnIfaceGlobal") m''
             let nsubst = mkNameShape (moduleName m) (mi_exports iface)
             case maybeSubstNameShape nsubst n of
-                Nothing -> failWithRn $ vcat [
-                    text "The identifier" <+> ppr (occName n) <+>
-                        -- NB: report m' because it's more user-friendly
-                        text "does not exist in the signature for" <+> ppr m',
-                    parens (text "Try adding it to the export list in that hsig file.")
-                    ]
+                -- NB: report m' because it's more user-friendly
+                Nothing -> failWithRn $ TcRnIdNotExportedFromModuleSig n m'
                 Just n' -> return n'
 
 -- | Rename an implicit name, e.g., a DFun or coercion axiom.
diff --git a/compiler/GHC/Tc/Errors/Ppr.hs b/compiler/GHC/Tc/Errors/Ppr.hs
index c629c5f5e4..90be5526b9 100644
--- a/compiler/GHC/Tc/Errors/Ppr.hs
+++ b/compiler/GHC/Tc/Errors/Ppr.hs
@@ -17,6 +17,7 @@ import GHC.Types.Error
 import GHC.Types.Name (pprPrefixName)
 import GHC.Types.Name.Reader (pprNameProvenance)
 import GHC.Types.SrcLoc (GenLocated(..))
+import GHC.Types.Name.Occurrence (occName)
 import GHC.Types.Var.Env (emptyTidyEnv)
 import GHC.Driver.Flags
 import GHC.Hs
@@ -55,6 +56,14 @@ instance Diagnostic TcRnMessage where
       -> mkDecorated [text "Use of plugins makes the module unsafe"]
     TcRnModMissingRealSrcSpan mod
       -> mkDecorated [text "Module does not have a RealSrcSpan:" <+> ppr mod]
+    TcRnIdNotExportedFromModuleSig name mod
+      -> mkDecorated [ text "The identifier" <+> ppr (occName name) <+>
+                       text "does not exist in the signature for" <+> ppr mod
+                     ]
+    TcRnIdNotExportedFromLocalSig name
+      -> mkDecorated [ text "The identifier" <+> ppr (occName name) <+>
+                       text "does not exist in the local signature."
+                     ]
     TcRnShadowedName occ provenance
       -> let shadowed_locs = case provenance of
                ShadowedNameProvenanceLocal n     -> [text "bound at" <+> ppr n]
@@ -183,6 +192,10 @@ instance Diagnostic TcRnMessage where
       -> WarningWithoutFlag
     TcRnModMissingRealSrcSpan{}
       -> ErrorWithoutFlag
+    TcRnIdNotExportedFromModuleSig{}
+      -> ErrorWithoutFlag
+    TcRnIdNotExportedFromLocalSig{}
+      -> ErrorWithoutFlag
     TcRnShadowedName{}
       -> WarningWithFlag Opt_WarnNameShadowing
     TcRnDuplicateWarningDecls{}
@@ -258,6 +271,10 @@ instance Diagnostic TcRnMessage where
       -> noHints
     TcRnModMissingRealSrcSpan{}
       -> noHints
+    TcRnIdNotExportedFromModuleSig name mod
+      -> [SuggestAddToHSigExportList name $ Just mod]
+    TcRnIdNotExportedFromLocalSig name
+      -> [SuggestAddToHSigExportList name Nothing]
     TcRnShadowedName{}
       -> noHints
     TcRnDuplicateWarningDecls{}
diff --git a/compiler/GHC/Tc/Errors/Types.hs b/compiler/GHC/Tc/Errors/Types.hs
index 282fccd1d6..82a908cf5a 100644
--- a/compiler/GHC/Tc/Errors/Types.hs
+++ b/compiler/GHC/Tc/Errors/Types.hs
@@ -175,7 +175,26 @@ data TcRnMessage where
      Test cases: None
   -}
   TcRnModMissingRealSrcSpan :: Module -> TcRnMessage
+  {-| TcRnIdNotExportedFromModuleSig is an error pertaining to backpack that occurs
+      when an identifier required by a signature is not exported by the module
+      or signature that is being used as a substitution for that signature.
 
+      Example(s): None
+
+     Test cases: backpack/should_fail/bkpfail36
+  -}
+  TcRnIdNotExportedFromModuleSig :: Name -> Module -> TcRnMessage
+  {-| TcRnIdNotExportedFromLocalSig is an error pertaining to backpack that
+      occurs when an identifier which is necessary for implementing a module
+      signature is not exported from that signature.
+
+      Example(s): None
+
+     Test cases: backpack/should_fail/bkpfail30
+                 backpack/should_fail/bkpfail31
+                 backpack/should_fail/bkpfail34
+  -}
+  TcRnIdNotExportedFromLocalSig :: Name -> TcRnMessage
 
   {-| TcRnShadowedName is a warning (controlled by -Wname-shadowing) that occurs whenever
       an inner-scope value has the same name as an outer-scope value, i.e. the inner
diff --git a/compiler/GHC/Types/Hint.hs b/compiler/GHC/Types/Hint.hs
index 364bad8355..be8417f19c 100644
--- a/compiler/GHC/Types/Hint.hs
+++ b/compiler/GHC/Types/Hint.hs
@@ -20,6 +20,7 @@ import Data.Typeable
 import GHC.Unit.Module (ModuleName, Module)
 import GHC.Hs.Extension (GhcTc)
 import GHC.Core.Coercion
+import GHC.Types.Name (Name)
 import GHC.Types.Basic (Activation, RuleName)
 import GHC.Parser.Errors.Basic
 import {-# SOURCE #-} Language.Haskell.Syntax.Expr
@@ -190,6 +191,9 @@ data GhcHint
   | SuggestAddInlineOrNoInlinePragma !Var !Activation
 
   | SuggestAddPhaseToCompetingRule !RuleName
+    {-| Suggests adding an identifier to the export list of a signature.
+    -}
+  | SuggestAddToHSigExportList !Name !(Maybe Module)
     {-| Suggests increasing the limit for the number of iterations in the simplifier.
 
     -}
diff --git a/compiler/GHC/Types/Hint/Ppr.hs b/compiler/GHC/Types/Hint/Ppr.hs
index abb30d55d8..ab3478d4c4 100644
--- a/compiler/GHC/Types/Hint/Ppr.hs
+++ b/compiler/GHC/Types/Hint/Ppr.hs
@@ -14,6 +14,7 @@ import GHC.Types.Hint
 
 import GHC.Hs.Expr ()   -- instance Outputable
 import GHC.Types.Id
+import GHC.Unit.Types
 import GHC.Utils.Outputable
 
 import Data.List (intersperse)
@@ -98,6 +99,11 @@ instance Outputable GhcHint where
          $$ text "    including the definition module, you must qualify it."
     SuggestTypeSignatureForm
       -> text "A type signature should be of form <variables> :: <type>"
+    SuggestAddToHSigExportList _name mb_mod
+      -> let header = text "Try adding it to the export list of"
+         in case mb_mod of
+              Nothing -> header <+> text "the hsig file."
+              Just mod -> header <+> ppr (moduleName mod) <> text "'s hsig file."
 
 perhapsAsPat :: SDoc
 perhapsAsPat = text "Perhaps you meant an as-pattern, which must not be surrounded by whitespace"
diff --git a/testsuite/tests/backpack/should_fail/bkpfail30.stderr b/testsuite/tests/backpack/should_fail/bkpfail30.stderr
index 7d332560f6..7c4b8c1fc3 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail30.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail30.stderr
@@ -3,4 +3,4 @@
 
 <no location info>: error:
     The identifier T does not exist in the local signature.
-    (Try adding it to the export list of the hsig file.)
+    Suggested fix: Try adding it to the export list of the hsig file.
diff --git a/testsuite/tests/backpack/should_fail/bkpfail31.stderr b/testsuite/tests/backpack/should_fail/bkpfail31.stderr
index ab599229ad..103e690943 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail31.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail31.stderr
@@ -5,4 +5,4 @@
 
 <no location info>: error:
     The identifier T does not exist in the local signature.
-    (Try adding it to the export list of the hsig file.)
+    Suggested fix: Try adding it to the export list of the hsig file.
diff --git a/testsuite/tests/backpack/should_fail/bkpfail34.stderr b/testsuite/tests/backpack/should_fail/bkpfail34.stderr
index cbe8a1bdbe..f1d5d03153 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail34.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail34.stderr
@@ -5,4 +5,4 @@
 
 <no location info>: error:
     The identifier T does not exist in the local signature.
-    (Try adding it to the export list of the hsig file.)
+    Suggested fix: Try adding it to the export list of the hsig file.
diff --git a/testsuite/tests/backpack/should_fail/bkpfail36.stderr b/testsuite/tests/backpack/should_fail/bkpfail36.stderr
index e031625aac..3ec5c6f56b 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail36.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail36.stderr
@@ -7,4 +7,4 @@
 
 <no location info>: error:
     The identifier T does not exist in the signature for <A>
-    (Try adding it to the export list in that hsig file.)
+    Suggested fix: Try adding it to the export list of A's hsig file.